An initial approach might be to survey other occurrences of the comparative "more" followed by a genitive. I'll start by introducing a notation to help compare structures, using (A, B, C) for people, (X, Y) for things, V for a verb and > for "more than":
Do you love me more than you love these things?
A loves me more than A loves X: AVC > AVX
Do you love me more than you love these other disciples?
A loves me more than A loves others: AVC > AVB
Do you love me more than these other disciples love me?
A loves me more than others love me: AVC > BVC
(An absurdity: Do you love me more than these things love me?)
A loves me more than X love me: AVC > XVC
And now, here are all the occurrences in the New Testament:
Mt 5:20
ἐὰν μὴ περισσεύσῃ ὑμῶν ἡ δικαιοσύνη πλεῖον τῶν γραμματέων καὶ Φαρισαίων
unless your propriety could exceed more than the theologians and separatists,
A has of X more than B has of X: AVX > BVX
Mt 12:41-42, Lk 11:31-32
καὶ ἰδοὺ πλεῖον Ἰωνᾶ ὧδε...καὶ ἰδοὺ πλεῖον Σολομῶνος ὧδε.
and look, more than Jonas here...and look, more than Solomon here.
A more than B: A > B
Mt 21:36
πάλιν ἀπέστειλεν ἄλλους δούλους πλείονας τῶν πρώτων,
again he sent other slaves more than the first
A sent more X than old A did: AVX > A'VX
Mt 26:53
καὶ παραστήσει μοι ἄρτι πλείω δώδεκα λεγιῶνας ἀγγέλων;
and will present to me just now more than twelve legions of angels?
A presents more than N X: AV(X > N)
Mk 12:43, Lk 21:3
ἡ χήρα αὕτη ἡ πτωχὴ πλεῖον πάντων ἔβαλεν
this beggar widow cast more than all
A cast X more than B cast X: AVX > BVX
Jn 21:15
ἀγαπᾷς με πλέον τούτων;
do you love me more than (?) these?
?
Ac 4:22
ἐτῶν γὰρ ἦν πλειόνων τεσσεράκοντα ὁ ἄνθρωπος
for the person was more than forty years
A was more than N X: NA > NX
Ac 23:13
ἦσαν δὲ πλείους τεσσεράκοντα
but they were more than forty
A was more than N X: NA > NX
Ac 23:21
ἐνεδρεύουσιν γὰρ αὐτὸν ἐξ αὐτῶν ἄνδρες πλείους τεσσεράκοντα,
for more than forty men of them lie in wait for him,
A was more than N X: NA > NX
Ac 25:6
Διατρίψας δὲ ἐν αὐτοῖς ἡμέρας οὐ πλείους ὀκτὼ ἢ δέκα,
but when he traveled among them not more than eight or ten days,
A traveled not more than N X: AV(X > N)
1 Cor 10:5
ἀλλ’ οὐκ ἐν τοῖς πλείοσιν αὐτῶν ηὐδόκησεν ὁ θεός
but God did not think highly in the more than them
A did not think highly in the more than B: AV in > B?
Php 1:14
καὶ τοὺς πλείονας τῶν ἀδελφῶν ἐν κυρίῳ...τολμᾶν
and the more of the brothers in lord...to dare
more A (than previously) to dare: (A > A')V
Re 2:19
Οἶδά...τὰ ἔργα σου τὰ ἔσχατα πλείονα τῶν πρώτων,
I have seen...your last works more than the first
A has seen...your last X more than A has seen your first X: AVX > AVY
however, this has also been read:
A has seen...your last X is more than your first X: AV(X > Y)
Summarizing:
- AVX > BVX (2)
- AVX > A'VX
- A > B
- AV(X > N) (2)
- NA > NX (3)
- AV in > B?
- B > AV
- AVX > AVY or possibly AV(X > Y)
Looking only at the options you identified:
- AVC > AVX: "Do you love me more than you love these things?" might be supported by Rev 2:19, although it has things as objects instead of people, but it has an alternate reading, too.
- AVC > AVB: "Do you love me more than you love these other disciples?" has even less support.
- AVC > BVC: "Do you love me more than these other disciples love me?", although it has no direct support of persons as the object, it has good support when things are the object. One might even include Mt 21:36, where actor "B" is actor "A" in the past.
- AVC > XVC: "Do you love me more than these things love me?" has no occurrences.
Therefore, although a more extensive survey of other contemporaneous works should be done, I'd lean mostly on option 3: "Do you love me more than these other disciples love me?"